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2 Chapter 1 Introduction to Chemistry CHAPTER 1 Visit the Chemistry Web site at chemistrymc.com to find links about chemistry and matter. The four nebulae shown here contain a stew of elements. The red color in two of the nebulae is emitted by hydrogen atoms. The Horsehead Nebula can be seen on the right. The fourth nebula is the bluish structure below the horse’s head. The round, bright object on the left is the star Zeta Orionis. What You’ll Learn You will describe the rela- tionship between chemistry and matter. You will recognize how sci- entific methods can be used to solve problems. You will distinguish between scientific research and technology. Why It’s Important You, and all the objects around you, are composed of matter. By studying matter and the way it changes, you will gain an understanding of your body and all the “stuff” you see and interact with in your everyday life.

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Page 1: Chapter 1: Introduction to Chemistry · 2 Chapter 1 Introduction to Chemistry CHAPTER 1 Visit the Chemistry Web site at chemistrymc.com to find links about chemistry and matter. The

2 Chapter 1

Introduction toChemistry

CHAPTER 1

Visit the Chemistry Web site atchemistrymc.com to find linksabout chemistry and matter.

The four nebulae shown herecontain a stew of elements. Thered color in two of the nebulae isemitted by hydrogen atoms. TheHorsehead Nebula can be seen onthe right. The fourth nebula isthe bluish structure below thehorse’s head. The round, brightobject on the left is the star ZetaOrionis.

What You’ll LearnYou will describe the rela-tionship between chemistryand matter.

You will recognize how sci-entific methods can be usedto solve problems.

You will distinguishbetween scientific researchand technology.

Why It’s ImportantYou, and all the objectsaround you, are composedof matter. By studyingmatter and the way itchanges, you will gain anunderstanding of your bodyand all the “stuff” you seeand interact with in youreveryday life.

▲▲

▲▲

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1.1 The Stories of Two Chemicals 3

DISCOVERY LAB

Materials

large kitchen matcheslaboratory balancelab notebookpenstopwatch or clock

Where is it?

When an object burns, the quantity of ashes that remain is smallerthan the original object that was burned. What happened to the

rest of the object?

Safety Precautions

Procedure

1. Measure the mass of a large kitchen match. Record this measure-ment and detailed observations about the match.

2. Carefully strike the match and allow it to burn for five seconds.Then, blow it out. CAUTION: Keep hair and loose clothing awayfrom the flame. Record observations about the match as it burnsand after the flame is extinguished.

3. Allow the match to cool. Measure and record the mass of theburned match.

4. Place the burned match in a container designated by your instructor.

5. Repeat this procedure. Compare your data from the two trials.

Analysis

How do you account for the change in mass? Where is the matterthat appears to have been lost?

Do not place matches in the sink. Use cautionaround flames.

Objectives• Explain the formation and

importance of ozone.

• Describe the developmentof chlorofluorocarbons.

Section 1.1 The Stories of Two Chemicals

Take a moment to look around you. Where did all the “stuff” you see comefrom? All the stuff in the universe is made from building blocks formed instars such as the ones shown in the photo on the opposite page. And, as youlearned in the DISCOVERY LAB, this stuff changes form.

Scientists are naturally curious. They continually ask questions about andseek answers to all that they observe in the universe. One of the areas in whichscientists work is the branch of science called chemistry. Your introductionto chemistry will begin with two unrelated discoveries that now form the basisof one of the most important environmental issues of our time.

The Ozone LayerYou are probably aware of some of the damaging effects of ultraviolet radi-ation from the Sun if you have ever suffered from a sunburn. Overexposureto ultraviolet radiation also is harmful to plants and animals, lowering cropyields and disrupting food chains. Living things can exist on Earth becauseozone, a chemical in Earth’s atmosphere, absorbs most of this radiation beforeit reaches Earth’s surface. A chemical is any substance that has a definite com-position. Ozone is a substance that consists of three particles of oxygen.

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Earth’s atmosphere As you can see in Figure 1-1, Earth’s atmosphere con-sists of layers. The lowest layer is called the troposphere and contains the airwe breathe. The troposphere is where the clouds shown in Figure 1-2 occurand where airplanes fly. All of Earth’s weather occurs in the troposphere.

The stratosphere is the layer above the troposphere. It extends from about15 to 50 kilometers (km) above Earth’s surface. The ozone that protects Earthis located in the stratosphere. About 90% of Earth’s ozone is spread out in alayer that surrounds and protects our planet.

Ozone formation How does ozone enter the stratosphere? Ozone (O3) isformed when oxygen gas is exposed to ultraviolet radiation in the upperregions of the stratosphere. Particles of oxygen gas are made of two smalleroxygen particles. The energy of the radiation breaks the gas particles into oxy-gen particles, which then interact with oxygen gas to form ozone. Figure 1-3 illustrates this process. Ozone also can absorb radiation and break apart toreform oxygen gas. Thus, there tends to be a balance between oxygen gas andozone levels in the stratosphere.

Ozone was first identified and measured in the late 1800s, so its presencehas been studied for a long time. It was of interest to scientists because aircurrents in the stratosphere move ozone around Earth. Ozone forms over theequator where the rays of sunlight are the strongest and then flows towardthe poles. Thus, ozone makes a convenient marker to follow the flow of airin the stratosphere.

In the 1920s, G.M.B. Dobson began measuring the amount of ozone in theatmosphere. Although ozone is formed in the higher regions of the stratosphere,most of it is stored in the lower stratosphere, where it can be measured byinstruments on the ground or in balloons, satellites, and rockets. Dobson meas-ured levels of stratospheric ozone of more than 300 Dobson units (DU). Hismeasurements serve as a basis for comparison with recent measurements.

During 1981–1983, a research group from the British Antarctic Survey wasmonitoring the atmosphere above Antarctica. They measured surprisingly lowlevels of ozone, readings as low as 160 DU, especially during the Antarcticspring in October. They checked their instruments and repeated their measure-ments. In October 1985, they reported a confirmed decrease in the amount ofozone in the stratosphere and concluded that the ozone layer was thinning.

4 Chapter 1 Introduction to Chemistry

Figure 1-1

Earth’s atmosphere consists ofseveral layers. The layer nearestEarth is the troposphere. Thestratosphere is above thetroposphere.

500

100

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Thermosphere

Exosphere

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(km

)

Mesosphere

Stratosphere

Troposphere

Figure 1-2

The troposphere extends toa height of about 15 km.Cumulonimbus clouds, or thun-derheads, produce thunder,lightning, and rain.

Topic: G.M.B. DobsonTo learn more about G.M.B.Dobson, visit the ChemistryWeb site at chemistrymc.comActivity: Research the workof G.M.B. Dobson. Make agraph of his measurementsby year.

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Figure 1-4

The thinning heel of thissock models the thinning of theozone layer in the stratosphere.

This colored satellite map ofstratospheric ozone overAntarctica was taken onSeptember 15, 1999. The lowestamount of ozone (light purple)appears over Antarctica (darkpurple). Blue, green, orange,and yellow show increasingamounts of ozone.

b

a

Although the thinning of the ozone layer is often called the ozone hole, itis not actually a hole. You can think of it as being similar to the old sock inFigure 1-4a in which the material of the heel is wearing thin. You might beable to see your skin through the thinning sock. So although the ozone is stillpresent in the atmosphere, the protective layer is much thinner than normal.This fact has alarmed scientists who never expected to find such low levels.Measurements made from balloons, high-altitude planes, and satellites havesupported the measurements made from the ground, as the satellite map inFigure 1-4b shows. What could be causing the ozone hole?

ChlorofluorocarbonsThe story of the second chemical in this chapter begins in the 1920s.Refrigerators, which used toxic gases such as ammonia as coolants, were justbeginning to be produced large scale. Because ammonia fumes could escapefrom the refrigerator and harm the members of a household, chemists beganto search for safer coolants. Thomas Midgley, Jr. synthesized the first chlo-rofluorocarbons in 1928. A chlorofluorocarbon (CFC) is a chemical that con-sists of chlorine, fluorine, and carbon. There are several different chemicalsthat are classified as CFCs. They are all made in the laboratory and do notoccur naturally. CFCs are nontoxic and stable. They do not readily react withother chemicals. At the time, they seemed to be ideal coolants for refrigera-tors. By 1935, the first self-contained home air-conditioning units and eightmillion new refrigerators in the United States used CFCs as coolants. In addi-tion to their use as refrigerants, CFCs alsowere used in plastic foams and as propellantsin spray cans.

1.1 The Stories of Two Chemicals 5

Figure 1-3

This model of the formation ofozone shows that ultravioletradiation from the Sun causesoxygen gas to break down intotwo individual particles of oxy-gen. These individual oxygenparticles combine with oxygengas to form ozone, which con-sists of three oxygen particles.

Oxygen gas

Formation of ozone

Ozone

Ultravioletradiation

a

b

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Now think of all the refrigerators in yourneighborhood, in your city, across the coun-try, and around the world. Think of the airconditioners in homes, schools, office build-ings, and cars that also used CFCs. Add toyour mental list all of the aerosol cans andplastic foam cups and food containers usedeach day throughout the world. If all of theseproducts contained or were made with CFCs,imagine the quantities of these chemicals thatcould be released into the environment in asingle day.

Scientists first began to notice the pres-ence of CFCs in the atmosphere in the 1970s.They decided to measure the amount of CFCsin the stratosphere and found that quantitiesin the stratosphere increased year after year.This increase is shown in Figure 1-5. But, itwas thought that CFCs did not pose a threatto the environment because they are so stable.

Two separate occurrences had been noticedand measured: the protective ozone layer in the atmosphere was thinning, andincreasingly large quantities of useful CFCs were drifting into the atmo-sphere. Could there be a connection between the two occurrences? Before youlearn the answer to this question, you need to understand some of the basicideas of chemistry and know how chemists—and most scientists, for thatmatter—solve problems.

6 Chapter 1 Introduction to Chemistry

CFC

-11

(pp

t)

280

240

200

160

120

Concentration of CFCs in the Atmosphere

19771979

19811983

19851987

19891991

19931995

Year

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0

1950

1960

1970

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October Ozone Concentrations

Ozo

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leve

l (D

U)

Section 1.1 Assessment

1. Why is ozone important in the atmosphere?

2. Where is ozone formed and stored?

3. What are CFCs? How are they used?

4. Thinking Critically Why do you think ozone isformed over the equator? What is the connectionbetween sunlight and ozone formation?

5. Comparing and Contrasting What generaltrend in ozone concentration is shown in the graphat the right? How does the data for the years1977–1987 on this graph compare to the sametime span on the graph in Figure 1-5? What doyou notice?

Figure 1-5

Quantities of CFCs in the atmo-sphere continued to rise until aban on products containingthem went into effect in manycountries.

chemistrymc.com/self_check_quiz

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Objectives• Define chemistry and

matter.

• Compare and contrast massand weight.

• Explain why chemists areinterested in a submicro-scopic description of matter.

Vocabularychemistrymattermassweight

Section Chemistry and Matter

Matter, the stuff of the universe, has many different forms. You are made ofmatter. There is matter in the bed, blankets, and sheets on which you sleep aswell as in the clothes you wear. There is matter in the food you eat, and inmedications and vitamins you may take. You have learned that ozone is a chem-ical that occurs naturally in the environment, whereas CFCs do not. Althoughboth chemicals are invisible gases, they, too, are matter.

Chemistry: The Central ScienceChemistry is the study of matter and the changes that it undergoes. A basicunderstanding of chemistry is central to all sciences—biology, physics, Earthscience, ecology, and others. Chemistry also is central to our everyday lives,as Figure 1-6 illustrates. It will continue to be central to discoveries made inscience and technology in the twenty-first century.

1.2

Figure 1-6

High-tech fabrics that don’t hinder athletic performance,water, fertilizers, pesticides,food, grocery items, clothing,building materials, hair careproducts, plastics, and even thehuman body are made of chemicals.

1.2 Chemistry and Matter 7

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Matter and its CharacteristicsYou recognize matter in the everyday objects you are familiar with, such asthose shown in Figure 1-6. But, how do you define matter? Matter is any-thing that has mass and takes up space. Mass is a measurement that reflectsthe amount of matter. It is easy to see that your textbook has mass and takesup space. Is air matter? You can’t see it and you can’t always feel it. However,when you inflate a balloon, it expands to make room for the air. The balloongets heavier. Thus, air must be matter. Is everything made of matter? Thethoughts and ideas that “fill” your head are not matter; neither are heat, light,radio waves, nor magnetic fields. What else can you name that is not matter?

Mass and weight When you go to the supermarket to buy a pound of veg-etables, you place them on a scale like the one shown in Figure 1-7 to findtheir weight. Weight is a measure not only of the amount of matter but alsoof the effect of Earth’s gravitational pull on that matter. This force is notexactly the same everywhere on Earth and actually becomes less as you moveaway from Earth’s surface at sea level. You may not notice a difference in theweight of a pound of vegetables from one place to another, but subtle differ-ences do exist.

It might seem more convenient for scientists to simply use weight insteadof mass. You might wonder why it is so important to think of matter in termsof mass. Scientists need to be able to compare the measurements that theymake in different parts of the world. They could identify the gravitational forceevery time they weigh something but that is not practical or convenient. Thisis why they use mass as a way to measure matter independent of gravitationalforce.

What you see and what you don’t What can you observe about the out-side of your school building or a skyscraper downtown? You know that thereis more than meets the eye to such a building. There are beams inside the wallsthat give the building structure, stability, and function. Consider another

8 Chapter 1 Introduction to Chemistry

problem-solving LAB

Chemical ModelsMaking Models Until the mid-1980s, scientiststhought there were only two forms of carbon,each with a unique structure: diamond andgraphite. As with many scientific discoveries,another form of carbon came as a surprise.

Buckminsterfullerene, also called the bucky-ball, was found while researching interstellarmatter. Scientists worked with various models ofcarbon structures until they determined that 60carbons were most stable when joined togetherin a shape that resembles a soccer ball.

AnalysisExamine the structure in the diagram. Where arethe carbon atoms? How many carbons is eachcarbon connected to? Identify the pentagons andhexagons on the faces on the buckyball.

Thinking CriticallyGo back to Figure 1-3 to see an example ofanother model that chemists use. What processdoes the figure show? Explain why this informa-tion could not be shown in a photograph. Whatdo the colored particles represent? Use Table C-1in Appendix C to help you in your identification.

Figure 1-7

A scale measures the downwardpull of gravity on an object. Ifthis scale were used on theMoon, the reading would be lessthan on Earth.

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example. When you bend your arm at the elbow, you observe that your handcomes toward your shoulder. Muscles that you cannot see under the skin con-tract and relax to move your arm.

Much of matter and its behavior is macroscopic; that is, you do not needa microscope to see it. You will learn in Chapter 3 that the tremendous vari-ety of stuff around you can be broken down into more than 100 types of mat-ter called elements, and that elements are made up of particles called atoms.Atoms are so tiny that they cannot be seen even with optical microscopes.Thus, atoms are submicroscopic. They are so small that 1 million millionatoms could fit onto the period at the end of this sentence.

The structure, composition, and behavior of all matter can be explained ona submicroscopic level. All that we observe about matter depends on atomsand the changes they undergo. Chemistry seeks to explain the submicro-scopic events that lead to macroscopic observations. One way this can be doneis by making a model, a visual representation of a submicroscopic event.Figure 1-3 is such a model. The problem-solving Lab on the opposite pagegives you practice interpreting a simple chemical model.

Branches in the field of chemistry Because there are so many types ofmatter, there are many areas of study in the field of chemistry. Chemistry istraditionally broken down into the five branches listed in Table 1-1.

Additional areas of chemisty include theoretical chemistry, which focuseson why and how chemicals interact, and environmental chemistry, whichdeals with the role chemicals play in the environment.

1.2 Chemistry and Matter 9

Section 1.2 Assessment

6. Define matter.

7. Compare and contrast mass and weight.

8. Why does chemistry involve the study of thechanges in the world at a submicroscopic level?

9. Thinking Critically Explain why a scientist mustbe cautious when a new chemical that has manypotential uses is synthesized.

10. Using Numbers If your weight is 120 poundsand your mass is 54 kilograms, how would thosevalues change if you were on the moon? The grav-itational force on the moon is 1/6 the gravitationalforce on Earth.

Branches of Chemistry

Branch Area of emphasis Examples

Organic chemistry Most carbon-containing chemicals Pharmaceuticals, plastics

Inorganic chemistry In general, matter that does not contain Minerals, metals and nonmetals, semi-carbon conductors

Physical chemistry The behavior and changes of matter and Reaction rates, reaction mechanismsthe related energy changes

Analytical chemistry Components and composition of substances Food nutrients, quality control

Biochemistry Matter and processes of living organisms Metabolism, fermentation

Table 1-1

Chemistry TeacherDo you love chemistry? Wouldyou like to help others loveit—or at least understand it? Ifso, you might make an excel-lent chemistry teacher.

Chemistry teachers work inhigh schools and two-year andfour-year colleges. They lec-ture, guide discussions, conductexperiments, supervise labwork, and lead field trips. Highschool teachers might also beasked to monitor study hallsand serve on committees.College instructors might berequired to do research andpublish their findings.

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Section 1.3 Scientific Methods

Objectives• Identify the common steps

of scientific methods.

• Compare and contrast typesof data.

• Compare and contrast typesof variables.

• Describe the differencebetween a theory and a scientific law.

Vocabularyscientific methodqualitative dataquantitative datahypothesisexperimentindependent variabledependent variablecontrolconclusionmodeltheoryscientific law

Figure 1-8 shows students working together on an experiment in the labora-tory. You know that each person in the group probably has a different ideaabout how to do the project and a different part of the project that interestshim or her the most. Having many different ideas about how to solve a prob-lem is one of the benefits of many people working together. Communicatingideas effectively to one another and combining individual contributions toform a solution can be difficulties encountered in group work.

A Systematic ApproachScientists approach their work in a similar way. Each scientist tries to under-stand his or her world based on a personal point of view and individual cre-ativity. Often, the work of many scientists is combined in order to gain newinsight. It is helpful if all scientists use common procedures as they conducttheir experiments.

A scientific method is a systematic approach used in scientific study,whether it is chemistry, biology, physics, or other sciences. It is an organizedprocess used by scientists to do research, and it provides a method for scien-tists to verify the work of others. An overview of the typical steps of a sci-entific method is shown in Figure 1-9. The steps are not used as a checklistto be done in the same order each time. Therefore, all scientists must describetheir methods when they publish their results. If other scientists cannot con-firm the results after repeating the method, then doubt arises over the valid-ity of the reported results.

Observation You make observations throughout your day in order to makedecisions. Scientific study usually begins with simple observation. An obser-vation is the act of gathering information. Quite often, the types of observa-tions scientists first make are qualitative data—information that describescolor, odor, shape, or some other physical characteristic. In general, anythingthat relates to the five senses is qualitative: how something looks, feels,sounds, tastes, or smells.

Figure 1-8

During your chemistry course,you will have opportunities touse scientific methods to per-form investigations and solveproblems.

10 Chapter 1

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Chemists frequently gather another type of data. For example, they canmeasure temperature, pressure, volume, the quantity of a chemical formed,or how much of a chemical is used up in a reaction. This numerical infor-mation is called quantitative data. It tells you how much, how little, howbig, how tall, or how fast. What kind of qualitative and quantitative data canyou gather from Figure 1-10?

Hypothesis Let’s return to the stories of two chemicals that you read aboutearlier. Even before quantitative data showed that ozone levels were decreas-ing in the stratosphere, scientists observed that CFCs were found there.Chemists Mario Molina and F. Sherwood Rowland were curious about howlong CFCs could exist in the atmosphere.

Molina and Rowland examined the interactions that can occur among var-ious chemicals in the troposphere. They determined that CFCs were stablethere for long periods of time. But they also knew that CFCs drift up into thestratosphere. They formed a hypothesis that CFCs break down in the strato-sphere due to interactions with ultraviolet light from the Sun. In addition, thecalculations they made led them to hypothesize that a chlorine particle pro-duced by this interaction would break down ozone.

A hypothesis is a tentative explanation for what has been observed. Molinaand Rowland’s hypothesis stated what they believed to be happening, eventhough there was no formal evidence at that point to support the statement.

Experiments A hypothesis means nothing unless there are data to support it.Thus, forming a hypothesis helps the scientist focus on the next step in a scien-tific method, the experiment. An experiment is a set of controlled observationsthat test the hypothesis. The scientist must carefully plan and set up one or morelaboratory experiments inorder to change and test onevariable at a time. A variableis a quantity or condition thatcan have more than one value.

Suppose your chemistryteacher asks your class touse the materials shown inFigure 1-11 to design anexperiment in which to testthe hypothesis that table saltdissolves faster in hot waterthan in water at room tem-perature (20°C).

Figure 1-9

The steps in a scientific methodare repeated until a hypothesishas been supported or dis-carded.

EXPE

RIMENTS

REVISED

CONCLU

SIONSHYPOTHESIS

REVISEDTHEORY

TH

EORY

EXPERIMEN

TS

THEORYHypothesissupportedby manyexperiments

SCIENTIFICLAW

Summary ofaccepted factsof nature

HYPOTHESISTestablestatement orprediction

OBSERVATIONSExisting knowledgeQualitative dataQuantitative data

Figure 1-10

Compare the qualitative andquantitative observations youcan make from this photo withyour classmates. Did you observethe same things?

11

LAB

See page 952 in Appendix E forTesting Predictions

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Because temperature is the variable that you plan to change, it is an independent variable. Your group determines that a given quantity of saltcompletely dissolves within 1 minute at 40°C but that the same quantity ofsalt dissolves only after 3 minutes at 20°C. Thus, temperature affects the rateat which the salt dissolves. This rate is called a dependent variable becauseits value changes in response to a change in the independent variable.Although your group can determine the way the independent variable changes,it has no control over the way the dependent variable changes.

What other factors could you vary in your experiment? Would the amountof salt you try to dissolve make a difference? The amount of water you use?Would stirring the mixture affect your results? The answer can be yes to all ofthese questions. You must plan your experiment so that these variablesare the same at each temperature, or you will not be able to tell clearly whatcaused your results. In a well-planned experiment, the independent variableshould be the only condition that affects the experiment’s outcome. A con-stant is a factor that is not allowed to change during the experiment. Theamount of salt, water, and stirring must be constant at each temperature.

In many experiments, it is valuable to have a control, that is, a standardfor comparison. In the above experiment, the room-temperature water is thecontrol. The rate of dissolving at 40°C is compared to the rate at 20°C.Figure 1-12 shows a different type of control. A chemical indicator has beenadded to each of three test tubes. Acid is added to the middle test tube, andthe indicator turns yellow. This test tube can be used as a control. Comparethe other two test tubes with the control. Does either one contain acid?

The interactions described between CFCs and ozone in Molina andRowland’s hypothesis take place high overhead. Many variables are involved.For example, there are different gases present in the stratosphere. Thus, itwould be difficult to determine which gases, or possibly if all gases, aredecreasing ozone levels. Winds, variations in ultraviolet light, and other fac-tors could change the outcome of any experiment on any given day makingcomparisons difficult. Sometimes it is easier to simulate conditions in a lab-oratory where the variables can be more easily controlled.

An experiment may generate a large amount of data. These data must becarefully and systematically analyzed. Because the concept of data analysisis so important, you will learn more about it in the next chapter.

Conclusion Scientists take the data that have been analyzed and apply themto the hypothesis to form a conclusion. A conclusion is a judgment based onthe information obtained. A hypothesis can never be proven. Therefore, to say

12 Chapter 1 Introduction to Chemistry

Figure 1-11

These materials can be used to determine the effect of temperature on the rate atwhich table salt dissolves.

Figure 1-12

The control test tube in the middle lets you make a visualcomparison.

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that the data support a hypothesis is to give only a tentative “thumbs up” tothe idea that the hypothesis may be true. If further evidence does not supportit, then the hypothesis must be discarded or modified. The majority ofhypotheses are not supported, but the data may still yield new information.

Molina and Rowland formed a hypothesis about the stability of CFCs inthe stratosphere. They gathered data that supported their hypothesis and devel-oped a model in which the chlorine formed by the breakdown of CFCs wouldreact over and over again with ozone. You must realize by now a model is avisual, verbal, and/or mathematical explanation of experimental data.

A model can be tested and used to make predictions. Molina and Rowland’smodel predicted the formation of chlorine and the depletion of ozone, asshown in Figure 1-13. Another research group found evidence of interactionsbetween ozone and chlorine when taking measurements in the stratosphere,but they did not know the source of the chlorine. Molina and Rowland’s modelpredicted a source of the chlorine. They came to the conclusion that ozone inthe stratosphere could be destroyed by CFCs and that they had enough sup-port for their hypothesis to publish their discovery.

Theory A theory is an explanation that has been supported by many, manyexperiments. You may have heard of Einstein’s theory of relativity or theatomic theory. A theory states a broad principle of nature that has been sup-ported over time. All theories are still subject to new experimental data andcan be modified. Also, theories often lead to new conclusions.

A theory is considered successful if it can be used to make predictions thatare true. In 1985, the announcement by the British Antarctic Survey that theamount of ozone in the stratosphere was decreasing lent Molina and Rowland’shypothesis—that chlorine from CFCs could destroy ozone—further support.

Scientific law Sometimes, many scientists come over and over again to thesame conclusion about certain relationships in nature. They find no excep-tions. For example, you know that no matter how many times skydivers leapfrom a plane, they always wind up back on Earth’s surface. Sir Isaac Newtonwas so certain that an attractive force exists between all objects that he pro-posed his law of universal gravitation.

Newton’s law is a scientific law and, as such, a relationship in nature thatis supported by many experiments. It is up to scientists to develop furtherhypotheses and experimentation to explain why these relationships exist.

1.3 Scientific Methods 13

Section 1.3 Assessment

11. What is a scientific method? What are its steps?

12. You are asked to study the effect of temperatureon the volume of a balloon. The balloon’s sizeincreases as it is warmed. What is the independentvariable? Dependent variable? What factor is heldconstant? How would you construct a control?

13. Critique Molina and Rowland’s hypothesis ofozone depletion as to its strengths and weaknesses.

14. Jacques Charles described the direct relationshipbetween temperature and volume of all gases at

constant pressure. Should this be called Charles’slaw or Charles’s theory? Explain.

15. Thinking Critically Why must Molina andRowland’s data in the laboratory be supported bymeasurements taken in the stratosphere?

16. Interpreting Data A report in the media statesthat a specific diet will protect individuals fromcancer. However, no data are reported to supportthis statement. Is this statement a hypothesis or aconclusion?

Figure 1-13

Molina and Rowland’s modelpredicted that ultraviolet radia-tion causes a chlorine particle tosplit off from a CFC.

The chlorine particle thendestroys the ozone by combin-ing with it to form oxygen gasand chlorine monoxide.

b

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Ultravioletradiation

OzoneChlorine

Chlorinemonoxide

Oxygen gas

Chlorine

CFC

b

a a

b

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14 Chapter 1 Introduction to Chemistry

Section 1.4 Scientific Research

Objectives• Compare and contrast pure

research, applied research,and technology.

• Apply knowledge of labora-tory safety.

Vocabularypure researchapplied researchtechnology

Every day in the media, whether it’s TV, newspapers, magazines, or theInternet, you are bombarded with the results of scientific investigations. Manydeal with the environment, medicine, or health. As a consumer, you are askedto evaluate the results of scientific research and development. How do scien-tists use qualitative and quantitative data to solve different types of scientificproblems?

Types of Scientific InvestigationsPure research seeks to gain knowledge for the sake of knowledge itself.Molina and Rowland conducted research on CFCs and their interactions withozone as pure research, motivated by curiosity. No environmental evidenceat the time indicated that there was a correlation to their model in the strato-sphere. Their research only showed that CFCs could speed the breakdown ofozone in a laboratory setting.

When the ozone hole was reported in 1985, scientists had made measure-ments of CFC levels in the stratosphere that supported the hypothesis thatCFCs could be responsible for the depletion of ozone. The pure research doneonly for the sake of knowledge became applied research. Applied researchis research undertaken to solve a specific problem. Scientists continue tomonitor the amount of CFCs in the atmosphere and the annual changes in theamount of ozone in the stratosphere. Applied research also is being done tofind replacement chemicals for the CFCs that are now banned. Read theChemistry and Society feature at the end of this chapter to learn aboutresearch into the human genome. What type of research does it describe?

Chance discoveries Sometimes, when a scientist plans research with aspecific goal in mind, he or she will conduct experiments and reach a con-clusion that is expected. Sometimes, however, the conclusion reached is fardifferent from what was expected. Some truly wonderful discoveries in sci-ence have been made unexpectedly.

The discovery of nylon is one example. In 1928, E.I. DuPont de Nemoursand Company appointed a young, 32-year-old chemist from Harvard,Wallace Carothers, as the director of its new research center. The goal wasto create artificial fibers similar to cellulose and silk. In 1930, Julian Hill,a member of Carothers’ team, dipped a hot glass rod in a mixture of solu-tions and unexpectedly pulled out long fibers such as the one shown inFigure 1-14. Carothers pursued the development of these fibers as a syn-thetic silk that could withstand high temperatures and eventually developednylon in 1934. Nylon’s first use was in a toothbrush with nylon bristles.During World War II, nylon was used as a replacement for silk in parachutes.Nylon is used extensively today in textiles and some kinds of plastics.

Students in the LaboratoryIn your study of chemistry, you will learn many facts about matter. You also willdo experiments in which you will be able to form and test hypotheses, gatherand analyze data, and draw conclusions.

When you work in the chemistry laboratory, you are responsible for yoursafety and the safety of the people working nearby. Table 1-2 on page 16 listssome safety rules that you must use as a guide each time you enter the lab.

BiologyCONNECTION

Many discoveries in science aremade quite unexpectedly.

Alexander Fleming is famous formaking two such discoveries. Thefirst occurred in 1922, when nasalmucus accidentally dripped ontobacteria that he had been grow-ing for research. Rather thanthrowing the culture plate away,he decided to observe it over thenext several days. He found thatthe bacteria died. As a result, hediscovered that lysozyme, a chem-ical in mucus and tears, helps pro-tect the body from bacteria.

Six years later, in 1928, Flemingfound that one of his plates ofStaphylococcus bacteria had beencontaminated by a greenish mold,later identified as Penicillium. Heobserved it carefully and saw aclear area around the mold wherethe bacteria had died. In this case,a chemical in the mold—peni-cillin—was responsible for killingthe bacteria.

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Chemists and all other scientists use these safety rules. Before you do theminiLAB at the bottom of this page or the CHEMLAB at the end of thischapter, read the procedures carefully. Which safety rules in Table 1-2apply?

1.4 Scientific Research 15

Figure 1-14

Strands of nylon can be pulledfrom the top layer of solutions.After its discovery, nylon wasused mainly for war materialsand was unavailable for homeuse until after World War II.

Developing Observation SkillsObserving and Inferring A chemist’s ability tomake careful and accurate observations is devel-oped early. The observations often are used tomake inferences. An inference is an explanationor interpretation of observations.

Materials petri dish (2), graduated cylinder,whole milk, water, vegetable oil, four differentfood colorings, toothpick (2), dishwashingdetergent

Procedure1. Add water to a petri dish to a height of

0.5 cm. Add 1 mL of vegetable oil.

2. Dip the end of a toothpick in liquid dishwash-ing detergent.

3. Touch the tip of the toothpick to the water atthe center of the petri dish. Record yourdetailed observations.

4. Add whole milk to a second petri dish to aheight of 0.5 cm.

5. Place one drop each of four different food col-orings in four different locations on the sur-face of the milk, as shown in the photo. Donot put a drop of food coloring in the center.

6. Repeat steps 2 and 3.

Analysis1. What did you observe in step 3?

2. What did you observe in step 6?

3. Oil, the fat in milk, and grease belong to aclass of chemicals called lipids. What can youinfer about the addition of detergent to dish-water?

miniLAB

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16 Chapter 1 Introduction to Chemistry

Safety in the Laboratory

1. Study your lab assignment before you come to thelab. If you have any questions, be sure to ask yourteacher for help.

2. Do not perform experiments without your teacher’spermission. Never work alone in the laboratory.

3. Use the table on the inside front cover of this text-book to understand the safety symbols. Read allCAUTION statements.

4. Safety goggles and a laboratory apron must be wornwhenever you are in the lab. Gloves should be wornwhenever you use chemicals that cause irritations orcan be absorbed through the skin. Long hair must betied back. See the photo below.

5. Do not wear contact lenses in the lab, even undergoggles. Lenses can absorb vapors and are difficult toremove in case of an emergency.

6. Avoid wearing loose, draping clothing and danglingjewelry. Bare feet and sandals are not permitted inthe lab.

7. Eating, drinking, and chewing gum are not allowedin the lab.

8. Know where to find and how to use the fire extin-guisher, safety shower, fire blanket, and first-aid kit.

9. Report any accident, injury, incorrect procedure, ordamaged equipment to your teacher.

10. If chemicals come in contact with your eyes or skin,flush the area immediately with large quantities ofwater. Immediately inform your teacher of the nature of the spill.

11. Handle all chemicals carefully. Check the labels of allbottles before removing the contents. Read the labelthree times:

• Before you pick up the container.• When the container is in your hand.• When you put the bottle back.

12. Do not take reagent bottles to your work area unlessinstructed to do so. Use test tubes, paper, or beakersto obtain your chemicals. Take only small amounts. Itis easier to get more than to dispose of excess.

13. Do not return unused chemicals to the stock bottle.

14. Do not insert droppers into reagent bottles. Pour asmall amount of the chemical into a beaker.

15. Never taste any chemicals. Never draw any chemicalsinto a pipette with your mouth.

16. Keep combustible materials away from open flames.

17. Handle toxic and combustible gases only under thedirection of your teacher. Use the fume hood whensuch materials are present.

18. When heating a substance in a test tube, be carefulnot to point the mouth of the test tube at anotherperson or yourself. Never look down the mouth of atest tube.

19. Do not heat graduated cylinders, burettes, orpipettes with a laboratory burner.

20. Use caution and proper equipment when handlinghot apparatus or glassware. Hot glass looks the sameas cool glass.

21. Dispose of broken glass, unused chemicals, and prod-ucts of reactions only as directed by your teacher.

22. Know the correct procedure for preparing acid solu-tions. Always add the acid slowly to the water.

23. Keep the balance area clean. Never place chemicalsdirectly on the pan of a balance.

24. After completing an experiment, clean and put awayyour equipment. Clean your work area. Make surethe gas and water are turned off. Wash your handswith soap and water before you leave the lab.

Table 1-2

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Benefits of ChemistryIt is easy to understand the purpose of applied research because it addressesa specific problem. It also is easier to see its immediate benefit. Yet, when asudden, unexpected event occurs in the world, whether it’s the ozone hole orthe AIDS epidemic, the first line of defense is to look at the pure researchthat has already been conducted.

The products that we use to make our lives easier and more comfortableare the result of technological applications of pure and applied research.Technology is the practical use of scientific information. It is concerned withmaking improvements in human life and the world around us. As Figure 1-15shows, advances in technology can benefit us in many ways.

1.4 Scientific Research 17

Figure 1-15

Nuclear power and artificiallimbs and joints are just a few ofthe technological advances thathave improved human life.

Section 1.4 Assessment

17. Compare and contrast pure research and appliedresearch.

18. What is technology? Is technology a product ofpure research or applied research? Explain.

19. Explain why it is important to read each CHEM-LAB and miniLAB before you come to class.

20. Thinking Critically Explain the reason behindeach of the following.

a. Wear goggles and an apron in the lab even ifyou are only an observer.

b. Report all accidents to your teacher.c. Do not return unused chemicals to the stock

bottle.21. Interpreting Scientific Diagrams What safety

precautions should you take when you see the fol-lowing safety symbols?

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Pre-Lab

1. Heat is the transfer of energy from a warmer objectto a cooler object. If an object feels warm to yourfinger, your finger is cooler than the object andenergy is being transferred from the object to yourfinger. In what direction does the energy flow if anobject feels cooler to you?

2. Your forehead is very sensitive to hot and cold.How can you use this fact to detect whether anobject is giving off or absorbing heat?

3. Read the entire CHEMLAB. It is important toknow exactly what you are going to do during allchemistry experiments so you can use your labora-tory time efficiently and safely. What is the prob-lem that this experiment is going to explore?

4. What typical steps in a scientific method will youuse to explore the problem? Write down the proce-dure that you will use in each experiment that youdesign. Be sure to include all safety precautions.

5. You will need to record the data that you collectduring each experiment. Prepare data tables thatare similar to the one below.

Rubber Band Data

Experiment # Observations

Trial 1

Trial 2

Trial 3

Trial 4

18 Chapter 1 Introduction to Chemistry

Safety Precautions

• Frequently observe the rubber band for any splits. Discard if rubber band isdefective.

• The hair dryer can become hot, so handle it with care.

ProblemWhat happens when youheat a stretched rubberband?

Objectives• Observe the properties of a

stretched and a relaxed rubber band.

• Form a hypothesis aboutthe effect of heat on astretched rubber band.

• Design an experiment totest your hypothesis.

• Collect and analyze data.• Draw conclusions based on

your analysis.

Materialslarge rubber band500-g massring standclamphair dryermeter stick or ruler

The Rubber Band StretchGalileo Galilei (1564–1642) was an Italian philosopher, astronomer,

and mathematician. Galileo pioneered the use of a systematicmethod of observation, experimentation, and analysis as a way todiscover facts about nature. Modern science has its roots in Galileo’s17th-century work on the art of experimentation. This chapter intro-duced you to how scientists approach their work. In this CHEMLAB,you will have a chance to design a scientific method to study some-thing you have observed many times before—the stretching of a rub-ber band.

CHEMLAB 1

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CHEMLAB 19

Procedure

1. Obtain one large rubber band. Examine the rubberband for any splits or cracks. If you find anydefects, discard it and obtain a new one.

2. Record detailed observations of the unstretchedrubber band.

3. Design your first experiment to observe whetherheat is given off or absorbed by a rubber band as itis stretched. Have your instructor approve yourplan.

4. Do repeated trials of your experiment until you aresure of the results. CAUTION: Do not bring therubber band near your face unless you are wearinggoggles.

5. Design a second experiment to observe whetherheat is given off or absorbed by a rubber band as itcontracts after being stretched. Have your instruc-tor approve your plan.

6. Do repeated trials of your experiment until you aresure of the results.

7. Use your observations in steps 2, 4, and 6 to forma hypothesis and make a prediction about what willhappen to a stretched rubber band when it isheated.

8. Use the remaining items in the list of materials todesign a third experiment to test what happens to astretched rubber band as it is heated. Have your

instructor approve your plan. Be sure to record allobservations before, during, and after heating.

Cleanup and Disposal

1. Return the rubber band to your instructor to bereused by other classes.

2. Allow the hair dryer to cool before putting it away.

Analyze and Conclude

1. Observing and Inferring What results did youobserve in step 4 of the procedure? Was energygained or lost by the rubber band? By your fore-head? Explain.

2. Observing and Inferring What results did youobserve in step 6 of the procedure? Was energygained or lost by the rubber band? By your fore-head? Explain.

3. Applying Many substances expand when they areheated. Did the rubber band behave in the sameway? How do you know?

4. Drawing a Conclusion Did the result of heatingthe stretched rubber band in step 8 confirm orrefute your hypothesis? Explain.

5. Making Predictions What would happen if youapplied ice to the stretched rubber band?

6. Compare your results and con-clusion with those of your classmates. What wereyour independent and dependent variables? Didyou use a control? Did all of the lab teams measurethe same variables? Were the data that you col-lected qualitative or quantitative? Does this make adifference when reporting your data to others? Doyour results agree? Why or why not?

Real-World Chemistry

1. When you put ice in a glass so that the ice riseshigher than the rim, water does not overflow theglass when the ice melts. Explain.

2. Why do you think temperature extremes must betaken into account when bridges and highways aredesigned?

Error Analysis

CHAPTER 1 CHEMLAB

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From eye and skin color to the potential for devel-oping disease, humans display remarkable and end-less variety. Much of this variety is controlled bythe human genome: the complete “instruction man-ual” found in the nucleus of all cells that is used todefine a specific organism. Decoding and under-standing these instructions is the goal of the HumanGenome Project (HGP). The United StatesDepartment of Energy and the National Institutesof Health coordinated the project that began in1990. Private industry also is involved. The HGPfosters cooperation as well as competition amongresearchers in a project that could hasten advancesin treatment of human genetic conditions such ascancer and heart disease.

A common goal, a commonapproachThe year 2003 marked the fiftieth anniversary ofWatson and Crick’s recognition of the structure ofDNA. Chemicals called nitrogen bases connect thetwisted strands that make up DNA. There areroughly three billion pairs of these bases in thehuman genome. Determining the sequence, ororder, in which these base pairs occur was one com-mon goal of researchers working on the HGP.Biologists, chemists, physicists, computer special-ists, and engineers across the country approach thetask from different angles. Use of scientific meth-ods was the unifying theme in all of this work.

Prior to the HGP, researchers around the worldused scientific methods to work independently onthe mammoth task of decoding the human genome.Without coordination, however, the data they col-lected were analyzed and stored using differentdatabases and were shared only through scientificjournals and conferences. Those working on theHGP used common methods for gathering and ana-lyzing data. Results were shared through databasesthat are rapidly available through the World WideWeb, enhancing communication, cooperation, andthe flow of information. Because of this coopera-tion, a rough map of the human genome was com-pleted in February 2001, several years ahead ofschedule. Efforts are underway to determine the

exact location of every gene, however, and resultswill have to be shared by researchers working onthe project.

Looking toward the futureThe HGP is spurring medical advances. But thispowerful knowledge also raises important issues.For example, if a person’s genome map shows apredisposition for a certain illness, should anemployer or insurance company be informed?While the HGP is opening exciting doors, the asso-ciated ethical, legal, and societal issues must beacknowledged and addressed.

1. Communicating Ideas Research some ofthe ethical, legal, and societal issues beingraised by genome research. Write a brief essaygiving your opinion about how one or more ofthese issues could be addressed.

2. Debating the Issue The race to sequence thehuman genome took place in both the publicand private sectors. Find information about sev-eral companies that worked independently ongenome research. Is it ethical for them to sellthis information, or should it be freely shared?

Investigating the Issue

The Human Genome Project

CHEMISTRY and

Society

Visit the Chemistry Web site atchemistrymc.com to find links to more informa-tion about the Human Genome Project.

20 Chapter 1 Introduction to Chemistry

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Study Guide 21

CHAPTER STUDY GUIDE1

Vocabulary

Summary1.1 The Stories of Two Chemicals• The building blocks of the matter in the universe

formed in the stars.

• A chemical is any substance that has a definitecomposition.

• Ozone is a chemical that forms a protective layer inEarth’s atmosphere.

• Ozone is formed in the stratosphere when ultravioletradiation from the Sun strikes oxygen gas.

• Thinning of the ozone layer over Antarctica is calledthe ozone hole.

• CFCs are synthetic chemicals made of chlorine, flu-orine, and carbon.

• CFCs were used as refrigerants and as propellants inaerosol cans.

• CFCs can drift into the stratosphere.

1.2 Chemistry and Matter• Chemistry is the study of matter and the changes

that it undergoes.

• Matter is anything that has mass and takes up space.

• Mass is a measure of the amount of matter.

• Weight is a measure not only of an amount of matterbut also the effect of Earth’s gravitational pull onthat matter.

• There are five traditional branches of chemistry:organic chemistry, inorganic chemistry, physicalchemistry, analytical chemistry, and biochemistry.

• Macroscopic observations of matter reflect theactions of atoms on a submicroscopic scale.

1.3 Scientific Methods• Typical steps of a scientific method include observa-

tion, hypothesis, experiments, data analysis, andconclusion.

• Qualitative data describe an observation; quantita-tive data use numbers.

• An independent variable is a variable that youchange in an experiment.

• A dependant variable changes in response to achange in the independent variable.

• A theory is a hypothesis that has been supported bymany experiments.

• A scientific law describes relationships in nature.

1.4 Scientific Research• Scientific methods can be used in pure research for

the sake of knowledge, or in applied research tosolve a specific problem.

• Laboratory safety is the responsibility of anyonewho conducts an experiment.

• Many of the conveniences we enjoy today are tech-nological applications of chemistry.

• applied research (p. 14)• chemistry (p. 7)• conclusion (p. 12)• control (p. 12)• dependent variable (p. 12)• experiment (p. 11)• hypothesis (p. 11)

• independent variable (p. 12)• mass (p. 8)• matter (p. 8)• model (p. 13)• pure research (p. 14)• qualitative data (p. 10)• quantitative data (p. 11)

• scientific law (p. 13)• scientific method (p. 10)• technology (p. 17)• theory (p. 13)• weight (p. 8)

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22 Chapter 1 Introduction to Chemistry

Go to the Chemistry Web site atchemistrymc.com for additional Chapter 1Assessment.

Concept Mapping22. Complete the concept map using the following terms:

stratosphere, oxygen gas, CFCs, ozone, ultravioletradiation.

Mastering Concepts23. What is a chemical? (1.1)

24. Where is ozone located in Earth’s atmosphere? (1.1)

25. Explain the balance between oxygen and ozone in thestratosphere. Why is it important? (1.1)

26. What were common uses of CFCs? (1.1)

27. What is chemistry? (1.2)

28. Why is chemistry called the central science? (1.2)

29. Which measurement depends on gravitational force—mass or weight? Explain. (1.2)

30. Which branch of chemistry studies the composition ofsubstances? Environmental impact of chemicals? (1.2)

31. How does qualitative data differ from quantitativedata? Give examples of each. (1.3)

32. What is the function of a control in an experiment? (1.3)

33. What is the difference between a hypothesis, a theory,and a law? (1.3)

34. In the study of water, what questions might be askedin pure research? Applied research? Technology? (1.4)

Thinking Critically35. Compare and Contrast Why is CFC depletion of

the ozone layer a theory and not a scientific law?

36. Classifying CFCs break down to form chemicals thatreact with ozone. Is this a macroscopic or a micro-scopic observation?

37. Communicating Ideas Scientists often learn asmuch from an incorrect hypothesis as they do fromone that is correct. Explain.

38. Designing an Experiment How would you designan experiment to evaluate the effectiveness of a “newand improved” chemical fertilizer on bean plants? Besure to describe your hypothesis, procedure, variables,and control.

39. Inferring A newscaster reports, “The air qualitytoday is poor. Visibility is only a quarter mile.Pollutants in the air are expected to rise above 0.085parts per million (ppm) in the next eight hour average.Spend as little time outside today as possible if yousuffer from asthma or other breathing problems.”Which of these statements are qualitative and whichare quantitative?

40. Comparing and Contrasting Match each of thefollowing research topics with the branch of chemistrythat would study it: water pollution, the digestion offood in the human body, the composition of a new tex-tile fiber, metals to make new coins, a treatment forAIDS.

Writing in Chemistry41. Based on your beginning knowledge of chemistry,

describe the research into depletion of the ozone layerby CFCs in a timeline.

42. Learn about the most recent measures taken by coun-tries around the world to reduce CFCs in the atmos-phere since the Montreal Protocol. Write a short reportdescribing the Montreal Protocol and more recentenvironmental measures to reduce CFCs.

43. Name a technological application of chemistry thatyou use everyday. Prepare a booklet about its discov-ery and development.

Cumulative ReviewIn chapters 2 through 26, this heading will be followedby questions that review your understanding of previouschapters.

CHAPTER ASSESSMENT1

is formedin the

when

breaks up

is destroyedby

1.

2. 5.

3.

4.

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Standardized Test Practice 23

Use these questions and the test-taking tip to preparefor your standardized test.

1. Matter is defined as anything that

a. exists in nature.b. is solid to the touch.c. is found in the universe.d. has mass and takes up space.

2. Mass is preferred as a measurement over weight for allof the following reasons EXCEPTa. it has the same value everywhere on Earth.b. it is independent of gravitational forces.c. it becomes less in outer space, farther from Earth.d. it is a constant measure of the amount of matter.

3. Which of the following is an example of pureresearch?

a. creating synthetic elements to study their propertiesb. producing heat-resistant plastics for use in house-

hold ovensc. finding ways to slow down the rusting of iron shipsd. searching for fuels other than gasoline to power

cars

4. When working with chemicals in the laboratory, whichof the following is something you should NOT do?

a. Read the label of chemical bottles before usingtheir contents.

b. Pour any unused chemicals back into their originalbottles.

c. Use lots of water to wash skin that has beensplashed with chemicals.

d. Take only as much as you need of shared chemicals.

Interpreting Tables and Graphs Use the table andgraph to answer questions 5–7.

5. What must be a constant during the experiment?

a. temperatureb. mass of CO2 dissolved in each samplec. amount of beverage in each sampled. independent variable

6. Assuming that all of the experimental data are correct,what is a reasonable conclusion for this experiment?

a. Greater amounts of CO2 dissolve in a liquid atlower temperatures.

b. The different samples of beverage contained thesame amount of CO2 at each temperature.

c. The relationship between temperature and solubil-ity seen with solids is the same as the one seenwith CO2.

d. CO2 dissolves better in a liquid at higher tempera-tures.

7. The scientific method used by this student showed that

a. the hypothesis is supported by the experimentaldata.

b. the observation accurately describes what occurs innature.

c. the experiment is poorly planned.d. the hypothesis should be thrown out.

STANDARDIZED TEST PRACTICECHAPTER 1

More Than One Graphic If a test questionhas more than one table, graph, diagram, or draw-ing with it, use them all. If you answer based onjust one graphic, you’ve probably missed an impor-tant piece of information. For questions 5-7 above,make sure that you accurately analyzed both graph-ics before answering the questions.

Page From a Student’s Laboratory Notebook

Step Notes

Observation Carbonated beverages taste fizzier(more gassy) when they are warmthan when they are cold. (Carbonatedbeverages are fizzy because theycontain dissolved carbon dioxide gas.)

Hypothesis At higher temperatures, greateramounts of carbon dioxide gas willdissolve in a liquid. This is the samerelationship between temperatureand solubility seen with solids.

Experiment Measure the mass of carbon dioxide(CO2) in different samples of thesame carbonated beverage at differenttemperatures.

Data Analysis See graph below.

Conclusion ?

0.35

0.30

0.25

0.20

0.15

0.100 5 10 15 20 25

Mass of CO2 Dissolved ina Carbonated Beverage

Temperature (˚C)

Mas

s o

f C

O2

(g)

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